The present invention relates to test signal generators, and more particularly to a component color bar alignment test signal applicable for aligning color component signals defined in Cartesian coordinates.
In calibrating a television system a picture monitor is used to subjectively observe signal quality. Therefore a first step in system calibration is to calibrate the picture monitor. To calibrate the picture monitor a test signal is inserted into the picture monitor and the chroma phase and gain are adjusted to achieve a desired appearance. For an NTSC picture monitor the test signal usually used is a SMPTE color bar test signal having a sequence of white, yellow, cyan, green, magenta, red, blue and black colors in the form of vertical bars of color. Below the color bars is a color set bar portion that matches different colors to the vertical color bars. For the NTSC composite video system a reverse blue bars is used as the color set bar portion so that bars containing blue alternate with black bars. To calibrate the picture monitor the red and green guns of the monitor are turned off. Chroma gain is adjusted to match the brightness of the color set bar portion just below the outer left or right blue bar. For chroma phase the brightness of either center main blue bar is adjusted to match the chroma set blue just below. For PAL systems chroma gain is calibrated in a similar manner, while small errors can be ignored since they can be removed in a full PAL decoder.
The conventional full field color bar alignment test signal for component video is designed to check GBR path gains in the picture monitor. This is a color primary system. However current monitors and component systems may use a luminance and color difference signals instead of GBR, namely Y, R-Y and B-Y or Y, Pb, Pr where Pb and Pr are normalized versions of B-Y and R-Y, respectively. The Pb and Pr chroma components define the color in orthogonal, or Cartesian, coordinates rather than polar coordinates. These new monitors have an internal matrix that converts the Y, Pb, Pr into GBR for the display, but current test signals do not provide a signal that is sensitive to gain adjustments in Cartesian coordinates.
What is desired is a test signal and calibration method for aligning a component picture monitor having Y, Pb and Pr as the component inputs.